It is known, in the technical sector relating to the production of switchboards for the wiring of electrical installations, to use terminal blocks designed to be mounted on associated supports, such as DIN-standard rails, and to provide on the front side access to the means—normally of the screw or spring type—for retaining electrical wires to be connected in order to restore continuity of the various sections of the electric circuit; said continuity being achieved by inserting inside a special seat, accessible from the front side, movable contact elements such as protection fuses, electric circuit breakers or jumpers for connecting together two or more adjacent terminal blocks.
It is also known that these connection jumpers may be:                configured with two spring lugs forming the element for coupling inside the seat of the terminal block assembly, with associated electrical contact in the longitudinal direction determined by the resilient force which pushes the lugs the walls of a hole in a longitudinal conductor lamina connecting together the means for retaining the electrical wires; or        of the screw type, with a conductor body in the form of an “overturned U”, providing electrical contact in the vertical direction by means of contact of the feet of the conductor body with the longitudinal conductor lamina connecting the opposite means for retaining the electrical wires, said contact being determined by tightening a screw inside the female thread of a hole formed in the said conductor lamina.        
The two types of connection jumper have different dimensional measurements both in the transverse direction of the width/thickness of the terminal block and in the longitudinal lengthwise direction of the terminal block.
It is also known that the increasingly greater demand for connections and branched junctions both in the electrotechnical sector and in the electronics sector, where it is required to direct also the control signals, results in the design of electric switchboards which have increasingly larger dimensions and consequently occupy a greater amount of space in the installation premises, resulting in greater costs due to the larger dimensions also of the installation cabinets.
EP 2 204 886 A1 describes a terminal block with a central space divided into two sub-spaces by a central dividing wall for receiving the separate legs of a shunt which may be for example a fuse, a relay or a signalling lamp. The configuration of the central space is such as to allow the insertion and subsequent extraction of the shunt in the vertical direction.
DE 10 2008 009986 describes a terminal block which has a detent lug corresponding to a detent hook of a detent arm formed near to a socket for a connection plug. The lug engages the detent hook of the detent arm in a reversibly locked condition of the connection plug in the socket, which plug may be extracted vertically from the socket by acting on the detent arm.
DE 295 02 186 U describes a terminal block assembly with means for reversible coupling in the direction of insertion of an electric connector.
All the cited documents illustrate electrical connection components to be inserted in a base terminal block, which by their very nature must be able to be subsequently extracted with ease from the base terminal block along the direction of insertion therein.
The technical problem which is posed, therefore, is to provide a terminal block, in particular of the type for wired-circuit switchboards, which allows the connection/branching capacity of the switchboard to be increased without having to increase its dimensions in particular in the longitudinal direction of the width, but preferably also thickness.
In connection with this problem, it is also required that this terminal block should have small dimensions and be able to be produced and assembled in an easy and low-cost manner and that it should be designed to avoid errors during the insertion of the different electrical contact jumpers with the consequent possibility of damage to the connected circuits.